Narcissistic Splitting:

Narcissistic splitting or inner splitting is a defense mechanism in which a person with narcissistic personality disorder (NPD) views people and situations in absolute, black-and-white terms (unable to see complexity in people and situations). Splitting can involve sudden shifting between idealization (seeing someone as perfect, high status, omnipotent — believing they’re entitled to special treatment) and devaluation (disliking or fearing a once-idealized person, now seeming them as worthless, defective, or dangerous). This cycle of extreme all-or-nothing thinking protects the narcissist’s unstable self-esteem by preventing them from integrating positive and negative traits, leading them to perceive others as either perfect or worthless. In this way, they avoid the anxiety of negative feelings or the possibility of being flawed, which affects their ability to maintain their grandiose self-image. Splitting is also associated with extreme emotions, including intense love, anger, or fear, as well as impulsive and risky behaviors. It tends to be triggered by trauma (early childhood experiences of abuse, neglect, or abandonment), PTSD and other mental health conditions (like borderline personality disorder), as well as by more minor events. Examples of splitting:

• In relationships: A narcissist might shower their love interest with compliments and love one moment, only to harshly criticize and devalue for a minor issue the next. (See Narcissistic Love-Bombing)
• Family dynamics: A narcissistic parent might label one child as “good” and another as “bad,” and these roles shift depending on the parent’s needs. 
• Self-view: A narcissist may deny their own mistakes or bad behavior, projecting these undesirable traits onto others